1. Field of the Invention
The present invention relates to image forming devices such as office machines, including facsimile machines, multi-function machines, and so on, which use a contact image sensor within a scanning device to scan a document, and, more particularly, to a contact image sensor fixing device for an office machine that can maintain a constant contact force between a contact image sensor and a corresponding sensor roller (referred to herein as a “white roller”), to enhance the quality of read out images.
2. Description of the Related Art
In general, an office machine such as a facsimile machine, a multi-function machine, and so on, has a scanning device to scan data recorded on documents, a facsimile device to transfer and receive scanned data through communication lines, and a printing device to print the scanned data, the data received through the communication lines, or data input from a computer on sheets of paper and to output the sheets. The scanner of the office machine is an essential device to transfer data recorded on documents or to print data on sheets of paper.
In FIG. 1, a general scanning device 10 is shown, which is used in an office machine such as a facsimile machine, a multi-function machine, and so on. Such a scanning device 10 has an automatic document transfer part 13 to automatically transfer documents D within the scanning device 10, a scanner 18 for reading out data from each of the documents D transferred by the automatic document transfer part 13, a white roller 19 for pressing each of the documents D against the scanner 18, and a discharge part 21 for discharging each of the documents D that has passed through the scanner 18 and the white roller 19.
The automatic document transfer part 13, which transfers each of the documents D inside the scanning device 10, has a document supply tray 15 in which documents D are loaded, a document load detector 1 for sensing whether the documents D are loaded, a pickup roller 14 for picking up each of the documents D according to operation of the document load detector 1, a friction pad 16 contacting the pickup roller 14 with a predetermined pressure to pick up the documents D sheet-by-sheet by friction, and a supply roller 14′ for transferring the documents D to the scanner 18.
The scanner 18 has a contact image sensor 23 (FIG. 2) to read out data from a document D transferred to the white roller 19 by a rotational force of the supply roller 14′.
As shown in FIG. 2 and FIG. 3, the contact image sensor 23 is fixed to a frame 25 of the scanning device by contact image sensor fixing devices 30 and 30′. The frame 25 rotatably supports shafts 20 and 20′ of the white roller 19.
The contact image sensor fixing devices 30 and 30′ have holders 32 and 32′ for accommodating and supporting the contact image sensor 23 and balancing the left and right ends of the contact image sensor 23 to enable smooth data readout operations. Hinge shafts 33 and 33′ provided in the respective holders 32 and 32′ are accommodated and supported in hinge shaft accommodation holes 34 and 34′ formed in the frame 25 so that the holders 32 and 32′ can be rotated. Elastic springs 35 and 35′ are mounted on respective spring seats 36 and 36′ of the frame 25 below the contact image sensor 23 to press the contact image sensor 23 in an upward direction so the scan glass face of the contact image sensor 23 can contact the surface of the white roller 19.
The holders 32 and 32′ have respective hook members 41 and 41′ coupled with hook member accommodation grooves 42 and 42′ formed in the contact image sensor 23 to fix the left and right ends of the contact image sensor 23.
The operations of the conventional scanning device 10 as illustrated in FIGS. 1 through 3 are described below.
First, when the documents D are loaded on the document supply tray 15, the documents D slide down due to the weight thereof, triggering an operation of the document load detector 1. Accordingly, a controller (not shown) applies electric power to a driving motor (not shown) to rotate the pickup roller 14.
The pickup roller 14, in concert with the friction pad 16, picks up one of the documents D by frictional force and transfers the picked-up document D to a document entry detector 17. When a user presses a start button of the office machine to transfer or copy data in the document D, the driving motor is driven again so that the supply roller 14′ conveys the document D toward the scanner 18.
Thereafter, as the supply roller 14′ conveys the document D between the scanner 18 and the white roller 19, the scanner 18 reads data from the document D. To read the data from the document, the contact image sensor 23 of the scanner 18 emits light through a light emitter (not shown) while contacting the white roller 19. Light is reflected from the document D to an optical sensor (not shown) as the document D is conveyed by the white roller 19. The output of the optical sensor is sent to an image process circuit (not shown).
The image process circuit compares the data output from the contact image sensor 23 with reference data to perform shading corrections and cording and compressing processes with respect to the corrected data, and sends the processed data to a facsimile device or a printing device for transferring or printing the processed data. To output the reference data, the contact image sensor 23 emits light to the white roller 19 through the light emitter before the document D is conveyed to the scanner 18, and the reference data are based upon the reflected light read by the optical sensor.
When the contact image sensor 23 completes the reading of the document data, the document D is externally discharged by the discharge part 21.
Because the scanning device 10 reads out data while the document D is conveyed onto the scanner 18, the contact image sensor 23 must be fixed at an exact position for the data to be read precisely from the document D. That is, the contact image sensor 23 must be positioned parallel to the white roller 19 for the scan glass face of the contact image sensor 23 to linearly contact the curved surface of the white roller 19.
However, for the contact image sensor 23 to contact the white roller 19, the conventional contact image sensor fixing devices 30 and 30′ are hingedly rotated by the hinge shafts 33 and 33′ of the holders 32 and 32′ within the hinge shaft accommodation holes 34 and 34′ of the frame 25. This causes a problem in that left and right pressures between the scan glass face of the contact image sensor 23 and the white roller 19 can be uneven due to machining and assembling variables such as the degree of flatness of the scan glass face of the contact image sensor 23 attached the holders 32 and 32′, the degree of precision of the positions of the hinge shafts 33 and 33′ of the holders 32 and 32′, the degree of precision of the hinge shaft accommodation holes 34 and 34′ of the frame 25, and so on.
As described above, if uneven left and right pressures are applied between the scan glass face of the contact image sensor 23 and the white roller 19, the contact image sensor 23 and the surface of the white roller 19 do not remain parallel to each other. Thus, the distances between the contact image sensor 23 and the white roller 19 become unequal along the length of the white roller 19, which adversely affects corrections of the document data.
Further, if the uneven left and right pressures are applied between the scan glass face of the contact image sensor 23 and the white roller 19, the document D may become skewed or obliquely conveyed by the white roller 19, resulting in the contact image sensor 23 not reading data precisely from the document D.